The goals of this proposal are to create a tumor antigen discovery system using human dendritic cells as antigen presenting cells and the most recent technological advances in in vitro culture of human T cells, to attempt to identify candidate tumor specific antigens. This is a novel approach in as much as all previous work in this area has been utilized secondary responses of T cells from cancer patients and tumor cells as antigen presenting cells. Recent evidence from several investigators point towards profound defects in cancer patients' T cell function, making this source less than optimal for defining potential tumor targets. We hypothesize that using naive T cells from healthy donors and a new, powerful in vitro priming system dependent on dendritic cells, should bypass the problem of tumor induced immune suppression in vivo and uncover all potential tumor antigens which have remained undetected in the recall responses. We will focus on lung cancer for which no specific antigens have been identified and on HLA-A2 restricting element, the most common human Class I allele. Emphasis will be placed on the ability of peptides, naturally processed by the tumor, to prime CD8+ T cell responses in vitro, when presented by dendritic cells. In addition, whole tumor proteins will be fractionated and then processed and presented by the dendritic cells to explore their potential of priming tumor-specific helped CD4+ T cell responses in vitro. One tumor antigen, MUC-1 mucin, that we have identified on breast and pancreatic adenocarcinomas is laos expressed by lung adenocarcinomas. Thus in addition to identifying new lung tumor antigens, we will test the full potential of lung tumor mucin to stimulate CD8+ and CD4+ T cells when presented by dendritic cells. Specific aims are: 1. To use dendritic cells as sensitive indicators of Class I restricted tumor specific that can prime CD8+ T responses in vitro. 2. To allow dendritic cells to take up and process tumor cell proteins and indicate those that can prime CD4+ T cell responses in vitro. Having shown the utility of this method, the ultimate goal of these studies will be to use the identified peptides and proteins for designing lung cancer vaccines or facilitating adoptive T cell therapy of lung cancer.